The present invention relates in general to powder paint transfer and distribution systems for use with powder coating applicators and, in particular, to a canister powder paint delivery apparatus and method for applying both multi-color powder (i.e. color key and or color specific) and single color powder.
In prior art systems, the powder paint is unloaded from a tote bulk storage system by a vacuum transport directly to a receiver. Alternatively, the powder paint is gravity fed from a bag bulk storage system into a vacuum stream. The unloaded powder in the receiver is then conditioned utilizing a sieve and gravity fed to a primary fluidized hopper. The powder paint is transferred from the primary hopper to a secondary fluidized hopper located approximately 25 feet from the point of application. The powder paint is fed from the secondary hopper or hoppers to the applicators. Disadvantageously, one complete distribution system that includes the bulk storage, sieve, primary hopper and secondary hopper is needed for each color of powder to be sprayed. Typically, one secondary hopper can supply six applicators, also a third level of hoppers is added for cut-ins and supplemental robotic application. Typically, there is one hopper per color of powder connected to each robot. This system requires that each color of powder have a series of hoppers, so that each color added to the system increases the number of primary, secondary, and robot hoppers required in the system. A venturi pumping system is used to transfer the powder paint material between the hoppers and the applicator. For example, a three color color-keyed and ten color color-specific system requires ten to thirteen primary hoppers, fifty to sixty secondary and/or robot hoppers, over one hundred fifty venturi pumps, and over twenty color changers.
It is desirable, therefore, to provide a simple, inexpensive, and efficient apparatus for supplying multi-color powder paint material to an applicator in a powder paint delivery system.
The present invention concerns an apparatus for supplying powder paint material to an applicator utilizing at least one canister; preferably a first and a second canister. Preferably each of the first and second canisters include a compressed air inlet and a dump line that is used for purging the canister of previously used powder so that a different color may be subsequently utilized for the same canister. The interiors of the first and second canisters define a fluidization air plenum therein. The plenum includes a porous plate disposed therein, which is connected to a fluidization air inlet and, when supplied with fluidization air, discussed in more detail below, fluidizes the powder paint in a well known manner.
The apparatus for at least two colors of powder includes at least two storage containers/hoppers each having at least two powder material outlets. Each of the at least two storage containers contain a different color powder material for use in a painting operation. The apparatus also includes at least two color changers each having at least two inlets and an outlet. A first one of the two inlets of each of the at least two color changers is connected to an associated one of the at least two outlets of a first one of the at least two storage containers/hoppers. A second one of the two inlets of each of the at least two color changers is connected to an associated one of the at least two outlets of a second one of the at least two storage containers/hoppers. The first and second canisters each have an inlet connected to the outlet of an associated one of the at least two color changers and an outlet. At least a third color changer includes at least two inlets each connected to an associated one of the outlets of the at least two canisters. The third color changer includes an outlet adapted to be connected to an applicator.
In operation, powder is sent from a hopper or bulk storage directly to one of the first and second color changers. The one of the first and second color changers opens an outlet valve for the correct color powder and allows the powder to flow into the canister. The powder is then pumped from the canister to the third color changer, which selects which of the first and second canisters is to feed the applicator.
While one of the first and second canisters is spraying powder, the other of the first and second canisters is cleaned and purged by opening the dump line and blowing the canister out with compressed air from the compressed air inlet. Once the canister is cleaned and purged, it is filled with the correct color of powder through the powder inlet. Prior to being sent to the applicator, the powder in the canister is kept in suspension by adding compressed air from the fluidization air inlet into the fluidization air plenum. The porous plate allows the air to pass, thus fluidizing the powder within the canister in a well known manner. Alternatively, the fluidization air may not be needed for the canister depending on the powder to be fluidized, the motion of the canister, and the duration the powder will be in the canister.
Alternatively, if the canister""s purge and fill process can be accomplished in the time allowed between painting vehicles, parts, or both, then only one canister may be required. Alternatively, the canisters can be sized to allow more than one applicator to be supplied by a single canister. The canisters can be sized advantageously to paint vehicles, parts, or both, in a batch method wherein one vehicle after another is painted with the same color.
The means for transferring powder paint from the storage containers/hoppers to the canisters and from the canisters to the applicator can be via a system that uses a vacuum transport, venturi pumps, or the like, or any other viable transfer means including, but is not limited to, a dense phase transfer system.
The method and apparatus according to the present invention is capable of supplying the powder paint directly from bulk storage to the applicators thereby reducing the number of hoppers and transfer equipment, which represents a very significant cost savings in automotive powder coating operations both in terms of capital and operating expense. A three color-keyed and ten color-specific system according to the present invention will advantageously eliminate the primary hoppers as well as the robot hoppers. Depending on the powder transport method used (i.e. dense phase), it may also be possible to eliminate the secondary hoppers allowing transfer of powder directly from the bulk storage to the applicator via the canister.